Boats on the Lake.
All the major towns on the lake are covered by the boat service and there is a regular service between then all. We stayed in Garda which is one of the oldest towns on the lake and seems to be the centre for the boat service.
The boat service is very reliable and mostly on time. This service is expensive if you are in a group, as we were. A short trip to Sirmione (approx 45 minutes on the boat) for 5 was 80 euros, the trip was very enjoyable and the water was calm. There are two different types of boats on the lake (the fast ones, which are the most expensive, and slower ones, which are less expensive) In my experience the slower ones are a more relaxed affair and arrive not long after the fast boats. All the boats are a good size and there is no need to stand, toilet facilities are clean. Some boats serve refreshments.
Check out the timetables carefully before you go a boat trip on the lake. You can always get a bus (or taxi) back! :-)